检查文本文件中访问的项目

我有一个读取文本文件中的项的代码。它逐行读取它们。当一个项目被读取时，它将被添加到一个列表中，以防止它再次被访问。当列表已满(最大大小)时，它将被清除。但是，有必要检查添加到列表中的项，以防止重新访问该特定项以获得预定义值，即使列表已清除。

请帮我弄清楚如何在c# 2012中做。

namespace SearchTechniques.Algorithms
{
using System;
using System.Collections.Generic;
public abstract class TSBase : SearchTechniquesBase
{
    // if Tabu list reaches the size (MaximumTabuListSize), it will be cleared.
    private readonly int MaximumTabuListSize = 8;
    public TSBase()
    {
        _tabuList = new List<object>();
    }
    protected override void RunAlgorithm(List<object> solutions)
    {
        _solutions = new List<object>();
        _tabuList.Clear();
        var solution = solutions[0];
        solutions.RemoveAt(0);
        while (solution != null)
        {
            _logger.Log("'t" + solution.ToString() + " - considering as next best solution not in tabu list based on cost function'n");
            _solutions.Add(solution);
            UpdateTabuList(solution);
            solution = FindNextBestSolution(solution, solutions);
            if (null != solution)
            {
                solutions.Remove(solution);
            }
        }
    }
    // updating tabu list
    private void UpdateTabuList(object solution)
    {
        _tabuList.Add(solution);
        if (_tabuList.Count >= MaximumTabuListSize)
        {
            _logger.Log("clearing tabu list as already reached: " + MaximumTabuListSize.ToString() + "'n");
            _tabuList.Clear();
        }
    }
    // finding the next best solution
    protected abstract object FindNextBestSolution(object solution, List<object> solutions);
    // the _solutions are both the list of current solutions and the tabu list in our case
    protected abstract bool SolutionExistsInTabuList(object solution);
    protected List<object> _tabuList;
}
 }

谢谢